It is known that such ventilating air intake arrangements are widely used in the aeronautical field for air renewal purposes in a confined zone containing thermally sensitive equipment and/or hazardous ambient media, of the flammable or explosive type, for which it is necessary to ensure continuous ventilation of the zone in order to avoid any risk of the equipment malfunctioning or of a surrounding incident.
Such is particularly the case with the numerous mechanical and/or electrical devices provided in the annular confined space or zone between the engine nacelle and the external fan casing and the compressors of an airplane jet engine. These devices, such as, for example, the fadec (full authority digital engine control), the gearbox, the engine oil tank, the fluid components, and so on, normally fixed all around the external casing and thus located in the confined zone, are ventilated by the external air entering into the arrangement through the air vent to pass through the channel provided in the nacelle and be diffused, on exiting from the channel, in the confined zone. The devices, just like the oil or other vapors emanating from this space, are ventilated by the external fresh air diffused by the air channel, which helps to ensure that they operate correctly.
To satisfy current regulations, which impose an appropriate air renewal rate per unit of time in the confined zone concerned, the air passage channel of the arrangement has a predetermined cross section allowing the circulation of a sufficient quantity of air in the channel to ensure, at its outlet, the renewal of air in the confined zone containing the devices to be ventilated.
However, the devices to be cooled and the vapors to be expelled are not ventilated optimally by the known air intake arrangements.
In practice, in these arrangements, while the outside air entering upstream through the air vent into the channel with predetermined cross section of the arrangement and exiting downstream of the latter is sufficient to correctly ventilate the devices when the aircraft is in the taxiing phase, in a take-off phase or in a waiting phase, and therefore at low speed, on the other hand, when the aircraft is in cruising flight phase at maximum speed and altitude, the quantity of air or the air flow rate exiting from the channel of the arrangement towards the zone to be ventilated is too great. This means that the devices are cooled too much, all the more so since the temperature of the external air is very low at this cruising altitude, which can lead to malfunctions. Measurements have, moreover, shown that, in this flight phase, the air circulating in the confined zone via the channel of the arrangement was renewed twice as much as necessary, such that the fadec, in particular, is cooled excessively, which can be prejudicial to its satisfactory operation.